This invention relates to drip irrigation tape and, specifically, to drip irrigation tape incorporating a pressure compensation feature.
Drip irrigation hose or tape has been available now for several years, and is used above and/or below ground. Typically, agricultural drip tapes are formed from relatively thin, flexible, continuous plastic strips folded over and seamed along a longitudinal edge to establish a primary flow path. One or more secondary flow paths are typically located adjacent the primary flow path by fixing discrete emitter devices along the length of the tape or hose, or by applying parallel strips of plastic material within the hose interior (for example, in the area of the longitudinal edge overlap) to form a secondary flow path. The tape is formed with inlets allowing water to move from the primary flow path to the secondary flow path, and outlets allowing water to flow from the secondary flow paths to atmosphere. In other words, water under pressure flows from the primary path to the secondary flow path, and then out of the drip tape in a controlled fashion. The secondary flow path reduces the pressure of the water so that it exits the tape outlets at essentially zero pressure. Some tape or hose constructions also incorporate turbulence inducing regions in the secondary flow path to prevent clogging and to reduce the sensitivity of the flow rate to pressure changes.
Drip irrigation hoses or tapes are well represented in the patent literature, and examples may be found in U.S. Pat. Nos. 3,870,236; 3,896,999; 4,009,832; 4,247,051; 4,430,020; 4,473,191; 4,874,132; 4,880,167; 4,984,739; 5,163,622; 5,181,532; 5,203,503; 5,207,386; 5,282,578; and 5,333,793. The incorporation of pressure compensation has also been attempted with varying degrees of success. Examples may be found in U.S. Pat. Nos. 3,993,248; 4,009,832 and 5,111,995. Relatively rigid discrete emitters have also been employed to provide a pressure compensation feature. See, for example, U.S. Pat. Nos. 4,210,287; 5,330,107; 5,609,303 and 5,813,603.
In commonly owned U.S. Pat. No. 5,688,072, a drip tape construction is disclosed wherein the tape is formed by a strip of flexible PE material folded over and seamed along overlapped longitudinal edges. Interiorly of the tape, and in an area remote from the overlapped seam, there is a longitudinally extending plastic bead or strip which incorporates a series of axially spaced secondary flow paths. Each secondary flow path has inlet, turbulence inducing, and outlet regions, all of which are preformed on one side of a hot melt bead or strip. The pattern or flow path side of the bead is applied face down on the strip so that the strip wall itself closes the secondary flow path except for a plurality of inlets formed in the bead at longitudinally spaced locations along the inlet region. These inlets are arranged perpendicular to the longitudinal axis of the tape, and thus also perpendicular to the secondary flow path. The inlets are located on both sides of the secondary flow path, in longitudinally spaced relationship.
The inlet region of each secondary flow path leads to a turbulence inducing region formed by a series of inwardly directed, projections on opposite sides of the secondary flow channel, in longitudinally offset relationship. This arrangement creates a tortuous path which induces turbulence in the water flowing along the secondary flow path, before exiting the tape.
Downstream of the turbulence inducing region, an outlet region is provided in the secondary flow path that communicates with an elongated slit in the tape wall which allows the water in the secondary flow path to escape in a controlled drip-like fashion. The outlet region, or reservoir, is otherwise axially closed in the downstream direction, thus isolating the path from the inlet region of the next adjacent downstream secondary flow path, and thus also forcing all water to exit via the elongated slit in the tape wall. This drip tape configuration does not, however, include any pressure compensation feature.
In accordance with one exemplary embodiment of this invention, a unique pressure compensation type drip tape includes a flexible tape or tubular member defining a primary flow path and a longitudinally extending pre-formed bead or strip incorporating multiple, axially oriented secondary flow paths. Each secondary flow path is formed in the strip or bead on three sides with the remaining open face sealed against the tape wall that forms the fourth side of the secondary flow path. Alternatively, the secondary flow path can face the interior of the tape and be sealed by a second strip with a flexible membrane located therebetween.
In either case, the secondary flow path is formed with inlet, turbulence inducing, pressure compensation and outlet regions. The inlet region may be substantially as shown in the commonly owned ""072 patent. The turbulence inducing region may include opposed, but axially offset triangularly shaped teeth that create a tortuous path for the water. This region may be formed as disclosed in expired U.S. Pat. No. 4,215,822. The pressure compensation region is located axially between the turbulence inducing region and the outlet region. It includes a pair of laterally spaced, ramped surfaces, preformed in the bead or strip, extending in a longitudinal direction. In the embodiment where the open faced bead is closed by the tape wall, the ramped surfaces taper from the secondary flow path toward the tape wall in the direction of flow. In the alternative embodiment, where the secondary flow path is closed by a second strip, the ramped surfaces taper toward the second strip in the flow direction. As pressure in the primary flow path rises, the ramped area will be forced to move toward the tape wall (the radially inner strip moves toward the ramped area in the alternative embodiment), thus restricting flow. The outlet region in both embodiments includes a longitudinal chamber with a plurality of axially spaced transverse ribs or other protrusions preventing unwanted shut-off of flow to the outlet. In a preferred embodiment, the chamber has a single slit outlet in the outlet chamber, but there may be circumstances where a pair of axially aligned outlet slits are useful as well.
In its broader aspects, therefore, the invention relates to irrigation drip tape comprising a flexible tubular member having an interior surface defining a primary flow path; a plurality of secondary flow paths provided on the interior surface, the secondary flow paths in substantially axially aligned relationship along a length dimension of the tubular member; each of the secondary flow paths comprising an inlet section, a turbulence-inducing-section, a pressure compensation section, and an outlet section, wherein the outlet section includes a chamber having side walls and upper and lower surfaces with one or more raised surfaces between the upper and lower surfaces to prevent the upper and lower surfaces from engaging; and at least one outlet in the tubular member in communication with the outlet chamber.
In another aspect, the invention relates to irrigation drip tape comprising a flexible tubular member having an interior surface defining a primary flow path; a plurality of secondary flow paths secured along the interior surface, the secondary flow paths in substantially axially aligned relationship along a length dimension of the tube; each of the secondary flow paths having an inlet region, a turbulence-inducing region, a pressure compensation region, and an outlet region including an outlet cut in the tubular member, wherein the outlet region includes a chamber having side walls and upper and lower surfaces, and means for preventing the upper and lower surfaces for engaging and shutting off flow to the outlet as a result of pressure in the primary flow path.
In still another aspect, the invention relates to irrigation drip tape comprising a flexible tubular member having an interior surface defining a primary flow path; a plurality of secondary flow paths provided on the interior surface, the secondary flow paths each having an inlet region including a plurality of inlet openings communicating with the primary flow path; a turbulence inducing region having a plurality of substantially triangular shaped teeth projecting alternatively from opposite sides of the secondary flow path, with points of the teeth lying substantially on a longitudinal centerline of the secondary flow path; a pressure compensation region; and an outlet region, the pressure compensation region including a pair of laterally spaced ramps between the turbulence inducing region and the outlet region; and wherein the outlet region includes a chamber having side walls and upper and lower surfaces with a plurality of axially spaced transverse ribs extending between the side walls; and at least one outlet slit in the tubular member in communication with the outlet chamber.
In yet another aspect, the invention relates to irrigation drip tape comprising a flexible tubular member having an interior surface and defining a primary flow path; at least one secondary flow path provided within the tube and isolated from the primary flow path, the secondary flow path having an upper surface, a lower surface and a pair of laterally spaced side walls; the upper surface bonded to the interior surface of the flexible tubular member, and wherein an elongated diaphragm is loosely confined between the lower surface and the secondary flow path; the secondary flow path having an inlet region including one or more inlets in the side walls to thereby permit water in the primary flow path to enter the secondary flow path; a turbulence inducing region downstream of the inlet region; a pressure compensation region downstream of the turbulence inducing region; and an outlet region downstream of the pressure compensation region, the outlet section including one or more outlets permitting water in the secondary flow path to emit to atmosphere, the outlet region including an elongated chamber incorporating means for preventing the diaphragm from engaging the upper surface.